Bi-directional actuator

Abstract

A thermally and electrically controllable miniaturised actuator comprises a bi-layer structure formed of a shape-memory alloy layer coupled with an electro-active polymer layer. A heating means is provided for thermal stimulation of the shape-memory alloy layer, this layer transitioning from an initial shape at a first temperature to a second, pre-determined, shape at a second temperature. Application of an electric field to the electro-active polymer layer stimulates this layer to deform in response, with a stress which may exceed that of the alloy layer, when the latter layer is in a low-temperature phase. Actuation methods are further provided, which include stimulating the polymer layer to deform in an opposite ‘direction’ to the deformation of the alloy layer, thus allowing the actuator to be ‘reset’ in between strokes. Methods of producing an actuator are also provided.

The invention claimed is: 
     
       1. A bi-directional actuator, comprising:
 a heat-sensitive shape-memory layer, wherein the heat-sensitive shape-memory layer comprises a shape memory alloy, the shape memory alloy existing in a first phase below a first temperature, and in a second phase above a second temperature, and wherein a transition from the first to the second phase stimulates the heat-sensitive shape-memory layer to move from any first shape into a second, predetermined shape; 
 an electro-active polymer layer, coupled with the heat-sensitive shape-memory layer such that both follow a same shape, the electro-active polymer layer being deformable, in response to an applied voltage; and 
 a heating means for controlling a temperature of the heat-sensitive shape-memory layer, wherein the heat-sensitive shape-memory layer and electro-active polymer layer provide bi-directional functionality in which the shape-memory alloy deforms with a first force on transition between the first phase to the second phase, wherein the first force provides an actuation force in a first direction, and in which the electro-active polymer layer provides a manual deformation of the shape-memory alloy back away from the second, pre-determined shape of the second phase, in a second direction, opposite the first direction, in response to an application of the applied voltage for a controlled speed and extent of the manual deformation in the second direction. 
 
     
     
       2. The actuator as claimed in  claim 1 , wherein the heating means comprises at least two contact terminals in electrical communication with the shape memory alloy, for delivery of an electrical current through the shape memory alloy. 
     
     
       3. The actuator as claimed in  claim 1 , wherein the heating means comprises a heating element in thermal communication with the heat-sensitive shape-memory layer. 
     
     
       4. The actuator as claimed in  claim 1 , wherein the heat-sensitive shape-memory layer comprises a layer of polymer material having an embedded shape memory alloy wire. 
     
     
       5. A beam-shaping element, comprising:
 a light-directing channel having one or more boundary walls, wherein at least one boundary wall comprises one or more of the actuators as claimed in  claim 1 ; and 
 a light source for emitting a beam within the light-directing channel. 
 
     
     
       6. A beam shaping element, comprising;
 a channel having one or more boundary walls, wherein at least one boundary wall comprises one or more actuator that comprises (i) a heat-sensitive shape-memory layer, wherein the heat-sensitive shape-memory layer includes a shape memory alloy, the shape memory alloy existing in a first phase below a first temperature, and a second phase above a second temperature, and wherein a transition from the first to the second phase stimulates the heat-sensitive shape-memory layer to move from any first shape into a second, predetermined shape, (ii) an electro-active polymer layer, coupled with the heat-sensitive shape-memory layer such that both follow a same shape, the electro-active polymer layer being deformable, in response to an applied voltage, and a heating means for controlling a temperature of the heat-sensitive shape-memory layer; and 
 one or more optical elements arranged at one end of the channel. 
 
     
     
       7. An adaptive lighting device comprising:
 one or more beam-shaping elements that comprise a channel having one or more boundary walls, wherein at least one boundary wall comprises one or more actuator that comprise (i) a heat-sensitive shape-memory layer, wherein the heat-sensitive shape-memory layer includes a shape memory alloy, the shape memory alloy existing in a first phase below a first temperature, and a second phase above a second temperature, and wherein a transition from the first to the second phase stimulates the heat-sensitive shape-memory layer to move from any first shape into a second, predetermined shape, (ii) an electro-active polymer layer, coupled with the heat-sensitive shape-memory layer such that both follow a same shape, the electro-active polymer layer being deformable, in response to an applied voltage, and a heating means for controlling a temperature of the heat-sensitive shape-memory layer; and 
 one or more solid-state lighting elements disposed within at least one boundary wall of the channel. 
 
     
     
       8. A skin-contacting structure for a skin-hair shaving device, the skin contacting structure for contacting a skin portion of a skin during shaving of said skin by the shaving device, the structure comprising an actuator for altering a relative position or orientation between at least a part of the skin contacting structure and the skin portion, wherein the actuator comprises (i) a heat-sensitive shape-memory layer, wherein the heat-sensitive shape-memory layer includes a shape memory alloy, the shape memory alloy existing in a first phase below a first temperature, and a second phase above a second temperature, and wherein a transition from the first to the second phase stimulates the heat-sensitive shape-memory layer to move from any first shape into a second, predetermined shape, (ii) an electro-active polymer layer, coupled with the heat-sensitive shape-memory layer such that both follow a same shape, the electro-active polymer layer being deformable, in response to an applied voltage, and a heating means for controlling a temperature of the heat-sensitive shape-memory layer. 
     
     
       9. A bi-directional actuation method, comprising:
 increasing, via a heating means, a temperature of a first layer element comprising that comprises a shape-memory alloy, above a transition temperature for stimulating the shape-memory alloy to transition from a first shape at a first temperature into a second, predetermined shape at a second temperature; 
 decreasing the temperature of the first layer element to a third temperature; and 
 applying a voltage to a second layer element, wherein the second layer element is coupled with the first layer element such that the first and second layer elements together follow a same shape, and wherein the second layer element comprises an electro-active polymer, for stimulating the electro-active polymer to deform from the second, pre-determined shape, into a third shape, the third shape dependent upon a magnitude of the voltage being applied, 
 wherein the shape-memory alloy of the first layer element and electro-active polymer of the second layer element provide bi-directional functionality in which the shape-memory alloy deforms with a first force in a first direction on transition between a first phase to a second phase, and in which the electro-active polymer provides a manual deformation of the shape-memory alloy back away from the second, pre-determined shape of the second phase, in a second direction, opposite the first direction, in response to an application of the voltage for a controlled speed and extent of the manual deformation in the second direction. 
 
     
     
       10. The method as claimed in  claim 9 , wherein the voltage is applied to the second layer element having a magnitude such that the third shape is identical to the first shape. 
     
     
       11. The method as claimed in  claim 9 , wherein the transition of the first layer element from the first shape to the second, predetermined shape, is used to deliver the first force, wherein the first force comprises an actuation force. 
     
     
       12. The method as claimed in  claim 9 , wherein the manual deformation provided by the electro-active polymer of the second layer element is used to deliver a second force that comprises an actuation force. 
     
     
       13. The method as claimed in  claim 9 , wherein the heating means comprises a joule heating process, and wherein a current is passed through at least a portion of the first layer element. 
     
     
       14. The method as claimed in  claim 9 , wherein the voltage is applied to the second layer element via the first layer element, wherein the first layer element is in electrical communication with the second layer element. 
     
     
       15. A method of producing a bi-directional actuator, comprising:
 coupling a first layer element that comprises a shape-memory alloy to a second layer element that comprises an electro-active polymer, such that the first and second layer elements together follow a same shape; and 
 providing a heating means in thermal communication with the first layer element, 
 wherein the shape-memory alloy exists in a first phase below a first temperature, and in a second phase above a second temperature, and wherein a transition from the first to the second phase stimulates the shape-memory alloy to move from any first shape into a second, predetermined shape, 
 wherein the electro-active polymer is deformable in response to an applied voltage, and 
 wherein the heating means controls the temperature of the shape-memory alloy, wherein the first layer element and the second layer element provide bi-directional functionality in which the shape-memory alloy deforms with a first force in a first direction on transition between the first phase to the second phase, and in which the electro-active polymer provides a manual deformation of the shape-memory alloy back away from the second, pre-determined shape of the second phase, in a second direction, opposite the first direction, in response to an application of the applied voltage for a controlled speed and extent of the manual deformation in the second direction.